It’s also, as Clegg must know perfectly well, true, but as Rod Liddle writes this week there are certain things you just can’t talk about, not just despite being true but because they’re true.

Rod cites what Dominic Grieve recently said about corruption, which was rude, offensive, insulting to the Pakistani community and of course totally true. Likewise when Richard Dawkins recently pointed out a fact about the relative success of the Muslim world vs Trinity College, Cambridge – that was offensive.

At some point in the English-speaking world it was agreed that people should not say things that were true, however necessary it might be, if it offended someone’s sacred identity. As an extension of this it was required that people stopped speculating on things that might offend, and so it became that the new Renaissance man was one totally incurious about the world.

There is difficulty defining this dulling of the western mind; the phrase ‘political correctness’ is unfortunate because even Right-wing head bangers like myself are bored with stories about Baa Baa Black Sheep being banned.

In the popular imagination PC is associated with euphemisms about race, sexuality, disability or any other perceived disadvantage, and as a consequence ‘politically incorrect’ is the same as rudeness. Indeed PC could be called ‘political politeness’. It’s impolite what Dominic Grieve said, and as a general rule things don’t get resolved if people are too polite to talk about them.

Political correctness comes from a secularised version of American Puritanism mixed with European Marxism; but the aim is not to pressure opponents into being polite, but to stop them expressing their ideas. PC had its origins in the moralistic atmosphere of American academia, where universities were traditionally affiliated to different churches, and academics who deviated from the doctrine of the faith were booted out.

After the Second World War a new faith, the radical Left, conquered all and academics who proposed vaguely controversial ideas, such as Richard Herrnstein or E.O. Wilson, became the victims of vicious student-led campaigns (Hernstein was talking about IQ and class in a meritocratic society, which is what BoJo was arguing). By the early 1980s British biologist Bill Hamilton wrote in his diaries of a wish to return home because the academic atmosphere in the US was becoming stifling.

And although America became less radical in the Nixon-Reagan era, academia became more so, especially when the students of 1968 returned as professors, and this political correctness, as it became known, fanned out into the wider culture of media and politics of the 1980s and 1990s. And it hasn’t gone away, you know.

Soon after Harvard alumni Jason Richwine stated that Hispanic school scores in the US had not improved in four generations, he was sacked by his think-tank and publicly disgraced. 1,200 Harvard students signed a petition calling for Richwine to have his doctorate taken away, and many of them wrote that even if his research was academically sound, and accurate, he should still be punished for studying things that might promote ‘discrimination and exclusion’. These are America’s future leaders.

Among those who poured scorn at Dawkins was one columnist who said that ‘only people like Dawkins’ would be interested in Trinity outscoring the entire Islamic world. ‘People like Dawkins’?…How, one wonders – being curious about things? Liberal academics such as Steven Pinker have become increasingly concerned about the stifling atmosphere in academia preventing the spirit of inquiry, and this undoubtedly filters out into public life in America and Britain.

Of the two Muslims who have won science Nobels, one is actually a member of the Ahmadiyya, an unorthodox, heavily persecuted and highly educated group from Pakistan. The Ahmadi want a new type of Islam because some of them argue that since the Golden Age the faith has abandoned the spirit of inquiry and has suffered as a result. What an offensive thing to believe. And totally true.